Vacuum Cleaners Vacuum-Cleaned (Jul, 1940)

This is so meta.

Vacuum Cleaners Vacuum-Cleaned
Because housewives generally hate to clean out vacuum-cleaner dust bags thoroughly, a Minneapolis, Minn., electrical shop does the job for them with a homemade machine. The bags are cleaned by a revolving brush set in an opening in a horizontal pipe, through which loosened dust is drawn off by a suction pump.

It’s not that housewives “hated” to clean out their vacuum bags: in the time before filters and disposable bags, they *couldn’t* clean them properly, and if they weren’t clean the vacuum wouldn’t work properly.